<!--
 * @由于个人水平有限, 难免有些错误, 还请指点:  
 * @Author: cpu_code
 * @Date: 2020-10-16 16:30:34
 * @LastEditTime: 2020-10-16 16:41:33
 * @FilePath: \web\javascript\js_number\js_number.html
 * @Gitee: [https://gitee.com/cpu_code](https://gitee.com/cpu_code)
 * @Github: [https://github.com/CPU-Code](https://github.com/CPU-Code)
 * @CSDN: [https://blog.csdn.net/qq_44226094](https://blog.csdn.net/qq_44226094)
 * @Gitbook: [https://923992029.gitbook.io/cpucode/](https://923992029.gitbook.io/cpucode/)
-->
<!DOCTYPE html>
<html>
    <head>
        <meta lang="UTF-8">
        <title>变量</title>
        <script>

            //定义变量
            /* var a  = 3;
            alert(a);

            a = "abc";
            alert(a);*/

            //定义number类型

            var num = 1;
            var num2 = 1.2;
            var num3 = NaN;

            //输出到页面上
            document.write(num + "<br>");
            document.write(num2 + "<br>");
            document.write(num3 + "<br>");

            //定义string类型
            var str = "abc";
            var str2 = 'aaa';

            document.write(str + "<br>");
            document.write(str2 + "<br>");

            //定义boolean
            var flag = null;
            document.write(flag + "<br>");

            // 定义null,undefined
            var obj = null;
            var obj2 = undefined;
            var obj3;

            document.write(obj + "<br>");
            document.write(obj2 + "<br>");
            document.write(obj3 + "<br>");
        </script>
    </head>

    <body>

    </body>
</html>